namespace Example
{
    using System.ServiceModel;

    [ServiceContract(Namespace = "http://example.net")]
    public interface ICalculator
    {
        [OperationContract]
        double Add(double operand1, double operand2);

        [OperationContract]
        double Divide(double operand1, double operand2);

        [OperationContract]
        double Multiply(double operand1, double operand2);

        [OperationContract]
        double Subtract(double operand1, double operand2);
    }
}